Syntax
SoilProfiles(PedotransferFunction, NumProfiles, P1NumLayers, P1H1Thickness, P1H1CoarseFragments, P1H1Parm1, P1H1Parm2, ..., P1h2Thickness, P1h2CoarseFragments, P1H2Parm1, ...)
Description
This function is used in conjunction with the MABIA Method for catchment hydrology and crop water requirements. Use the Soil Profiles Wizard, available on the drop-down menu in the data grid, to build this function.
Because direct measurement of a soil's water holding capacity, including saturation, field capacity and wilt point, can be costly and time consuming, pedotransfer functions were developed to translate more easily obtainable data into these water holding capacity values. The SoilProfiles function estimates average soil water capacity (saturation, field capacity and wilt point) using one of seven available pedotransfer functions (PTF), in order to determine the Soil Water Capacity for catchment branches in the Data View, under Land Use. This function can average over several soil profiles (sampling sites) and soil horizons (layers). (As an alternative to using SoilProfiles, you can enter soil properties directly, or choose a texture class from the Soil Library. These two options are also available on the drop-down menu in the data grid.)
PedotransferFunction: Of the seven available pedotransfer functions, one is based on texture class and the other six use particle size (sand, silt and clay), optionally with data on bulk density or organic matter content. The PTF names (which include references to the original author and date) used in the SoilProfiles function, along with the parameters required by that function, are:
"Texture class": texture class, from the Soil Library
"Particle size (Jabloun and Sahli 2006)": silt[%] and clay[%] fraction (sand is calculated as 100 - silt - clay, so does not need to be entered)
"Particle size Bulk density (Jabloun and Sahli 2006)": silt[%], clay[%] and bulk density[g/cm^3]
"Particle size Organic matter (Jabloun and Sahli 2006)": silt[%], clay[%] and organic matter[g/kg]
"Particle size Bulk density Organic matter (Jabloun and Sahli 2006)": silt[%], clay[%], bulk density[g/cm^3] and organic matter[g/kg]
"Particle size Bulk density Organic matter (Vereecken et. al. 1989)": silt[%], clay[%], bulk density[g/cm^3] and organic matter[g/kg]
"Particle size Bulk density Organic matter (Wösten et. al. 1999)": silt[%], clay[%], bulk density[g/cm^3] and organic matter[g/kg]
NumProfiles: The number of soil profiles (sampling sites) included.
PiNumLayers: The number of horizons (layers) in profile i.
PiHjThickness: The thickness (in meters) of profile i, horizon j.
PiHjCoarseFragments: Fraction of profile i, horizon j that is coarse fragments. Coarse fragments (rock) cannot hold any moisture--therefore, the higher the fraction of coarse fragments, the lower the water holding capacity.
PiHjParm_k: PTF parameter k for profile i, horizon j. Each PTF has its own parameters, described above.
Note: The MABIA Method will NOT use rooting depth to determine which soil horizons are in contact with the roots. Instead, the average soil water properties will be used regardless of root depth.
References
Jabloun, M. and Sahli, A., Development and comparative analysis of pedotransfer functions for predicting characteristic soil water content for Tunisian soil, Tunisia-Japan Symposium on Society, Science and Technology proceeding, 7th Edition, 2006, pp. 170-178.
Vereecken, H., Maes, J., Feyen, J., Darius, P., Estimating the soil moisture retention characteristic from texture, bulk density and carbon content, Soil Science, 148 (1989), pp. 389–403.
Wösten, J.H.M., Lilly, A., Nemes, A., Le Bas, C., 1999, Development and use of a database of hydraulic properties of European soils, Geoderma, 90, July 1999, pp. 169-185.
Examples
SoilProfiles("Texture class", 1, 2, 0.5, 5, Loam, 0.5, 10, Clay loam)
This example specifies one soil profile with two horizons, each 0.5m thick. The top horizon is Loam with 5% coarse fragments; the lower horizon is Clay loam, with 10% coarse fragments. The average soil properties are: Saturation = 38.17%, Field Capacity = 27.01%, Wilt Point = 12.64%, Available Water Capacity = 14.37%
SoilProfiles("Particle size Organic matter (Jabloun and Sahli 2006)", 2, 2, 0.3, 10, 20, 40, 5, 0.7, 20, 35, 35, 3, 1, 1, 15, 15, 70, 2)
This example specifies two soil profiles, the first with two horizons and the second with one horizon. The method used to compute soil water capacity is from Jabloun and Sahli, 2006, and requires particle size and organic matter content, in addition to thickness and coarse fragments. Profile 1, top horizon: 0.3m thick, 10% coarse fragments, 20% clay, 40% silt, 5 g/kg Organic Matter. Profile 1, lower horizon: 0.7m thick, 20% coarse fragments, 35% clay, 35% silt, 3 g/kg Organic Matter. Profile 2: 1.0m thick, 15% coarse fragments, 15% clay, 70% silt, 2 g/kg Organic Matter. The average soil properties are: Saturation = 35.03%, Field Capacity = 37.54%, Wilt Point = 13.20%, Available Water Capacity = 24.34%